At 362 kilometres (225 miles) south of Galveston, Texas, the Perdido oil and gas platform in the Gulf of Mexico is a long way from the customers who need the energy it produces. Moored in 2,450 metres (8,000 feet) of water, it represents a new frontier in oil and gas production.

Its distance from shore meant that laying pipelines to land would be too costly. Shell decided to connect Perdido to the nearest existing pipeline system, which served other platforms 128km (80 miles) away.

But the plan posed its own challenge: the existing pipeline lacked a port for connecting to other pipelines. Engineers would have to cut an opening safely into the 46cm (18 inch) line and build a connection.  Tapping into an undersea oil pipeline nearly 1,400 metres (almost a mile) deep had never been tried before.

Perdido deep water platform
Perdido deep-water project, Gulf of Mexico, USA, 2010

Going to great lengths

With pressure on the sea floor too great for human divers, the Perdido engineering team used remote-controlled submarine robots to perform the difficult task of connecting the new and existing pipelines.

Controlled from the surface, these 300-hp remotely-operated vehicles (ROVs) supplied by Oceaneering International can reach depths of over 3,000 metres (10,000 feet). They are about the size of a large car. Yet their articulated arms can handle delicate tasks such as turning valves and programming control panels. Their video and lighting systems provided a clear view of the action; operators often used them in tandem, positioning one to provide an alternative viewing angle while the other manipulated tools or performed other tasks.

The first task was to make the operation safe. After closing the existing pipeline, they installed a clamp to seal the pipe instantly if anything went wrong as they cut into it. They also installed pumps and an undersea storage system to capture any leakage. A containment dome capped the working area as a further precaution.

It took two and a half years of designing, planning and training to reach the point where the connection work could begin. The patience and attention to detail paid off. When the robots carried out the operation, not a single drop of oil leaked from the pipe.

Close encounters

As the remotely-operated machines descended into the darkness, they encountered rarely seen sea creatures such as the magnapinna big fin squid. Most cephalopods have eight short arms and two long tentacles. This species, caught on camera at 2km (1.24 miles) beneath the surface, had ten tentacles of the same length dangling from elbow-like joints. An undulating fin looked like an alien’s head.

The squid appeared to have appendages 5-10 metres (16-33 feet) long. Despite its size, the species’ existence had been unknown until then. Perdido’s pipeline had to be routed to avoid disturbing other deep-sea inhabitants. These included a chemosynthetic colony-pale crabs and other bizarre creatures that feed on oil seeping naturally from the sea floor.

Marine biologists involved in deep-sea research now commonly work with Shell to access its technically-advanced equipment and video footage.

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